The Water Cycle

What is the water cycle?

The hydrological cycle is a closed system and is the continuous movement of water on, above and below Earth's surface

Why is the water cycle important?

• The Goldilocks Zone - this is how Earth in just the right distance from the sun to allow the presence of liquid water, allowing the perfect amount of radiation to reach Earth

• The water supports life on earth, allowing a habitable environment since temps is regulated via the water cycle which evaporation is a part of allowing for photosynthesis and respiration.

What does water help create?

The thermal conditions on Earth - oceans moderate temperatures by absorbing heat, storing it and releasing it slowly.

What percentage of Earth’s surface do oceans cover?

71%

What are clouds made up of?

Tiny water droplets and ice crystals

What do clouds reflect and how much?

Reflect 1/5 of incoming solar radiation and lower surface temperatures

What does water vapour absorb?

It absorbs long-wave radiation from the Earth helping to maintain average global temperatures almost 15 degrees higher than it would be. (Greenhouse gas)

What percentage of water makes up all living organisms?

65-95%

What do flora and fauna need water for?

• Flora: photosynthesis, respiration and transpiration. They also require water for rigidity and transportation of minerals.

• Fauna: For a medium, used for all chemical reactions like the circulation of oxygen.

How does the planet support life?

• Atmosphere: Earth’s atmosphere is breathable, it has plenty of oxygen (21%) small amounts of CO2

• Climate: The temps on Earth don’t go from one extreme to another

• Water: Its drinkable and it allows life-providing molecules to move around easily

• Light: Photosynthesis

• Sun: Goldilocks zone ad Sun’s gravity keeps Earth in its orbit

What type of system is the water cycle?

Closed system between the atmosphere, oceans, land and biosphere - fixed amount of water in the system

What is the time scale of the cycling of water molecules cycling?

Can vary diurnally to millions of years

What are the macro-scale stores?

Atmosphere (smallest), Oceans (biggest), Land

How does water move inbetween the stores?

Precipitation, evapotranspiration, run-off and growundwater flow

What is the residence times of the macro stores?

• Atmosphere - 10 days

• Oceans - 3000 years

• Land - variable

What is the water cycle driven by? (Global scale)

The Sun’s energy

Why is the local water cycle in drainage basins or forests considered open systems?

Materials and the sun’s energy cross system boundaries

What’s a key store in the WC that holds 97% of all of the planet’s water?

Ocean

What percentage of freshwater is frozen in ice caps?

3/4 in Antarctica and Greenland

Where is 1/5 of freshwater found?

In rocks

How much does water does the water cycle, cycle per year?

505,000 km3 between principle water stores

What are the main outputs of the water cycle?

• Water vapor from oceans, soils, lakes, rivers and trees (evapotranspiration)

• Moisture also leaves as the atmosphere as precipitation through condensation.

• Ice sheets, glaciers and snowfield release water by ablation

• Precipitation and meltwater drain from the land surface as run-off into rivers. Most rivers flow to oceans and some drylands.

Where does most precipitation end up? Where does it end up after?

• Reaches rivers and infiltrating and flowing through the soil - percolation to permeable rocks or aquifers.

• This groundwater eventually reaches the surface as springs or seepages and contributes to run-off.

What percentage of Earth’s water is freshwater?

2.5%

What percentage of freshwater is available to humans?

0.9%